Don't use iron wire for your aerial.
Don't fail to insulate it well at both ends.
Don't have it longer than 75 feet for sending out a 200-meter wave.
Don't fail to use a lightning arrester, or better, a lightning switch, for your receiving set.
Don't fail to use a lightning switch with your transmitting set.
Don't forget you must have an outside ground.
Don't fail to have the resistance of your aerial as small as possible. Use stranded wire.
Don't fail to solder the leading-in wire to the aerial.
Don't fail to properly insulate the leading-in wire where it goes through the window or wall.
Don't let your aerial or leading-in wire touch trees or other objects.
Don't let your aerial come too close to overhead wires of any kind.
Don't run your aerial directly under, or over, or parallel with electric light or other wires.
Don't fail to make a good ground connection with the water pipe inside.

TRANSMITTING DON'TS

Don't attempt to send until you get your license.
Don't fail to live up to every rule and regulation.
Don't use an input of more than ½ a kilowatt if you live within 5 nautical miles of a naval station.
Don't send on more than a 200-meter wave if you have a restricted or general amateur license.
Don't use spark gap electrodes that are too small or they will get hot.
Don't use too long or too short a spark gap. The right length can be found by trying it out.
Don't fail to use a safety spark gap between the grid and the filament terminals where the plate potential is above 2,000 volts.
Don't buy a motor-generator set if you have commercial alternating current in your home.
Don't overload an oscillation vacuum tube as it will greatly shorten its life. Use two in parallel.
Don't operate a transmitting set without a hot-wire ammeter in the aerial.
Don't use solid wire for connecting up the parts of transmitters. Use stranded or braided wire.
Don't fail to solder each connection. Don't use soldering fluid, use rosin.
Don't think that all of the energy of an oscillation tube cannot be used for wave lengths of 200 meters and under. It can be if the transmitting set and aerial are properly designed.
Don't run the wires of oscillation circuits too close together.
Don't cross the wires of oscillation circuits except at right angles.
Don't set the transformer of a transmitting set nearer than 3 feet to the condenser and tuning coil.
Don't use a rotary gap in which the wheel runs out of true.

RECEIVING DON'TS

Don't expect to get as good results with a crystal detector as with a vacuum tube detector.
Don't be discouraged if you fail to hit the sensitive spot of a crystal detector the first time--or several times thereafter.
Don't use a wire larger than No. 30 for the wire electrode of a crystal detector.
Don't try to use a loud speaker with a crystal detector receiving set.
Don't expect a loop aerial to give worthwhile results with a crystal detector.
Don't handle crystals with your fingers as this destroys their sensitivity. Use tweezers or a cloth.
Don't imbed the crystal in solder as the heat destroys its sensitivity. Use Wood's metal, or some other alloy which melts at or near the temperature of boiling water.
Don't forget that strong static and strong signals sometimes destroy the sensitivity of crystals.
Don't heat the filament of a vacuum tube to greater brilliancy than is necessary to secure the sensitiveness required.
Don't use a plate voltage that is less or more than it is rated for.
Don't connect the filament to a lighting circuit. Don't use dry cells for heating the filament except in a pinch.
Don't use a constant current to heat the filament, use a constant voltage.
Don't use a vacuum tube in a horizontal position unless it is made to be so used.
Don't fail to properly insulate the grid and plate leads. Don't use more than 1/3 of the rated voltage on the filament and on the plate when trying it out for the first time.
Don't fail to use alternating current for heating the filament where this is possible.
Don't fail to use a voltmeter to find the proper temperature of the filament.
Don't expect to get results with a loud speaker when using a single vacuum tube.
Don't fail to protect your vacuum tubes from mechanical shocks and vibration.
Don't fail to cut off the A battery entirely from the filament when you are through receiving.
Don't switch on the A battery current all at once through the filament when you start to receive.
Don't expect to get the best results with a gas-content detector tube without using a potentiometer.
Don't connect a potentiometer across the B battery or it will speedily run down.
Don't expect to get as good results with a single coil tuner as you would with a loose coupler.
Don't expect to get as good results with a two-coil tuner as with one having a third, or tickler, coil.
Don't think you have to use a regenerative circuit, that is, one with a tickler coil, to receive with a vacuum tube detector.
Don't think you are the only amateur who is troubled with static.
Don't expect to eliminate interference if the amateurs around you are sending with spark sets.
Don't lay out or assemble your set on a panel first. Connect it up on a board and find out if everything is right.
Don't try to connect up your set without a wiring diagram in front of you.
Don't fail to shield radio frequency amplifiers. Don't set the axes of the cores of radio frequency transformers in a line. Set them at right angles to each other.
Don't use wire smaller than No. 14 for connecting up the various parts.
Don't fail to adjust the B battery after putting in a fresh vacuum tube, as its sensitivity depends largely on the voltage.
Don't fail to properly space the parts where you use variometers.
Don't fail to put a copper shield between the variometer and the variocoupler.
Don't fail to keep the leads to the vacuum tube as short as possible.
Don't throw your receiving set out of the window if it howls. Try placing the audio-frequency transformers farther apart and the cores of them at right angles to each other.
Don't use condensers with paper dielectrics for an amplifier receiving set or it will be noisy.
Don't expect as good results with a loop aerial, or when using the bed springs, as an out-door aerial will give you.
Don't use an amplifier having a plate potential of less than 100 volts for the last step where a loud speaker is to be used.
Don't try to assemble a set if you don't know the difference between a binding post and a blue print. Buy a set ready to use.
Don't expect to get Arlington time signals and the big cableless stations if your receiver is made for short wave lengths.
Don't take your headphones apart. You are just as apt to spoil them as you would a watch.
Don't expect to get results with a Bell telephone receiver.
Don't forget that there are other operators using the ether besides yourself.
Don't let your B battery get damp and don't let it freeze. Don't try to recharge your B battery unless it is constructed for the purpose.

STORAGE BATTERY DON'TS

Don't connect a source of alternating current direct to your storage battery. You have to use a rectifier.
Don't connect the positive lead of the charging circuit with the negative terminal of your storage battery.
Don't let the electrolyte get lower than the tops of the plates of your storage battery.
Don't fail to look after the condition of your storage battery once in a while.
Don't buy a storage battery that gives less than 6 volts for heating the filament.
Don't fail to keep the specific gravity of the electrolyte of your storage battery between 1.225 and 1.300 Baumé. This you can do with a hydrometer.
Don't fail to recharge your storage battery when the hydrometer shows that the specific gravity of the electrolyte is close to 1.225.
Don't keep charging the battery after the hydrometer shows that the specific gravity is 1.285.
Don't let the storage battery freeze.
Don't let it stand for longer than a month without using unless you charge it.
Don't monkey with the storage battery except to add a little sulphuric acid to the electrolyte from time to time. If anything goes wrong with it better take it to a service station and let the expert do it.

EXTRA DON'TS

Don't think you have an up-to-date transmitting station unless you are using C.W.
Don't use a wire from your lightning switch down to the outside ground that is smaller than No. 4.
Don't try to operate your spark coil with 110-volt direct lighting current without connecting in a rheostat.
Don't try to operate your spark coil with 110-volt alternating lighting current without connecting in an electrolytic interrupter.
Don't try to operate an alternating current power transformer with 110-volt direct current without connecting in an electrolytic interrupter.
Don't--no never--connect one side of the spark gap to the aerial wire and the other side of the spark gap to the ground. The Government won't have it--that's all.
Don't try to tune your transmitter to send out waves of given length by guesswork. Use a wavemeter.
Don't use hard fiber for panels. It is a very poor insulator where high frequency currents are used.
Don't think you are the only one who doesn't know all about wireless. Wireless is a very complex art and there are many things that those experienced have still to learn.